Electronic equipment, such as a mobile communication device or a mobile computing device, is subject to various electronic tests after production. Such tests are generally necessary to ensure proper configuration, calibration and functionality of various elements of the devices under test (DUT). For testing purposes, specific test apparatus are employed which simulate a testing environment under predefined testing conditions. Of particular relevance are tests and test apparatus for electronic equipment which is operated in an environment sensitive to radio frequency (RF) signals. Such equipment may be used to output, receive, measure or otherwise process RF-sensitive parameters and signals.
For the testing, specific cables, such as RF coaxial cables, are connected to channel terminals of the test apparatus. In reality, these cables are different with regard to their physical properties, in particular with regard to their length, electrical resistance, type and the like. Consequently, when using these cables during the testing the resulting attenuation is more or less different, even though cables of the same type and/or the same length are used. For highly sensitive test apparatus, such as RF test apparatus, this is not acceptable since due to the variation of the attenuation the test results are no more reliable. Therefore, modern RF test apparatus have to be calibrated before the testing is started.
WO 2012/084028 A1 discloses a calibration module for a RF test apparatus. The calibration module comprises a mode selector which is configured to switch between a measurement mode and a calibration mode. A separate calibration module is provided for calibration of a RF channel based on measurement signals.